Gear generating machine



Aug- 6, 1963 N. K. HAASE ETAL 3,09 39 GEAR GENERATING MACHINE Filed June 1'7, 1960 4 Sheets-Sheet l INVENTORSI NELSON K. HAASE BY ROBERT F. PIGAGE adv/41% ATTORNEY Aug. 6, 1963 N. K. HAASE ETAL GEAR GENERATING MACHINE 4 Sheets-Sheet 2 Filed June 17, 1960 NQI Aug. 6, 1963 N. K. HAASE ETAL GEAR GENERATING MACHINE 4 Sheets-Sheet '5 Filed June 17. 1960 ROTATION OF GEAR OR CRADLE FIG.5

Aug. 6, 1963 N. K. HAASE ETAL GEAR GENERATING MACHINE 4 Sheets-Sheet 4 Filed June 17. 1960 6 R-4 HQ GRI 3-,b-h9fi39 Patented Aug. 6, 1963 3,099,939 GEAR GENERATING MACHINE Nelson K. Haase and Robert F. Pigage, Rochester, N.Y., assignors to The Gleason Works, Rochester, N.Y., a corporation of New York Filed June 17, 1960, Ser. No. 36,991 18 Claims. (Cl. 90-3) The present invention relates to generating machines for spiral bevel and hypoid gears, including pinions having only one or a few teeth.

An object of the invention is a machine capable of producing high quality pinions of usual tooth number, i.e. five or more teeth, and also of low tooth number, to wit pinions having from one to four teeth.

A further object is a machine adapted to produce a onetooth pinion, substantially in the form of a worm, adapted to drive a one-tooth gear at varying velocity ratio. A related object is to produce such a one-tooth pinion with its tooth slot narrower at the center than at the ends, for the purpose of reducing backlash when the mesh is at the center.

The foregoing and other objects and advantages will appear from the following description of the preferred embodiment of the invention shown in the accompanying drawings, wherein:

FIG. 1 is a perspective view of the machine;

FIG. 2 is a drive diagram of the machine;

FIG. 3 is a bottom plan view of the feed mechanism for effecting relative advance and withdrawal between the cutter and workpiece;

FIG. 4 is an elevation of a pinion having a single tooth slot adapted to be cut on the machine and a one-tooth gear segment meshing with the pinion;

FIG. 5 is a diagram illustrating the varying velocity ratio of the pinion and gear segment, and the relationship between pinion generation and action of the feed mechanism of the machine; and

FIG. 6 is an electrical circuit diagram of the machine.

Referring to FIG. 1, the machine comprises a frame 10 on which a cradle 11 is rotatable about horizontal axis 12, the cradle suporting a cutter spindle 13, FIG. 2, for rotation thereon about axis 14. By adjustments which form no part of the present invention, the axis 14 may be placed in parallel or angular or skew relation to axis 12. A cutter carried by spindle 13 is adapted to generate one or both sides of the tooth or teeth of a workpiece W mounted on a work spindle 15. The latter is rotatable about axis 16 in a work head 17 that is adjustable vertically (as indicated by arrow 18) on a. column 19 which, in turn, is adjustable horizontally (as indicated by arrow 20) on a swinging base 21. This base is adjustable angularly (as shown by arrow 22) on a sliding base 23 about vertical axis 24 which intersects both axes 12 and 16 at right angles. The sliding base is adjustable and also movable during machine operation on the frame 10 in a horizontal direction (the direction of arrow 25) parallel to cradle axis 12. By these several adjustments the workpiece W may be brought into the desired relation to this axis and the cutter C.

Referring to FIG. 2, the cutter spindle 13 is driven by main motor 26 through bevel gears 27, gears 28, speed change gears 29, and gears 31 which are so arranged as to accommodate the aforementioned adjustments of spindle 13 on the cradle 11. The cradle 11 is connected to the work spindle by a generating train identified in FIG. 2 by heavy broken line 30. This train comprises a ring gear 33 on the cradle and a drive pinion 34 therefor, shaft 35, gears 35 and 37, a differential gear set comprising gears 38, 39 and 40 of which side gear 38 is connected to adjacent gear 3-7 and side gear 40 is secured to shaft 41,

ratio-of-roll change gears 42, shaft 43, a differential gear set comprising gears 44, 45, 46 of which side gear 44 is on shaft 43, bevel gears 7 of which one is integral with side gear 45, bevel gears 48, telescoping overhead shaft 49 (also see FIG. 1), bevel gears 51, vertical telescoping shaft 52, bevel gears 53, index change gears 54, pinion 55, and gear 56 on spindle 15. The differential gear sets are for introducing additional motions into the generating train, the set 38, 39, 44 for the purpose of modifying the ratio of roll between the work spindle and the cradle, and the set 44, 45, 46 for indexing the work spindle.

The generating train may be driven, as in now-conventional machines, by the main motor 26 through a unidirectionally rotating drum cam 57 having a track 58, FIG. 3, which acts to rotate the generating train alternately back and forth. The drum cam is driven, from previously mentioned gears 29, through rate-of-feed change gears 59 and fixed-ratio gears 61, aligned shafts 62, gears 63, shaft 64, gears 65 and 66, pinion 67, and gear 68 on the drum cam. A follower 69 for track 58 of the cam is carried by a gear sector 76' pivoted at 71 to frame 10, so that during each complete revolution of the cam the sector is given one oscillation about its pivot. This motion is transmitted to the generating train through a pinion '72 meshing with the sector, gears 73, angle-of-roll change gears 74, and gears '75 of which one is affixed to shaft 35.

For indexing the work spindle between the cutting of successive teeth or successive tooth slots, an intermittent drive from shaft 64 to the carrier of differential planet gear 45 is provided. This drive comprises bevel gears 7 6 and 77, telescoping shaft 78, Geneva drive element 79 and driven wheel 81, gear 82 and gear =83, the latter being keyed to the carrier of the differential planet gear. This index mechanism, which may be substantially as disclosed in detail in Patent No. 2,869,427 to L. O. Carlsen et al., is arranged to advance the work spindle angularly once for each revolution of cam 57. A cam, not shown in the present drawings, is preferably provided to shift driver 79 axially in and out of engageable relation to driven wheel 81, permitting he driver to make a plurality of turns during each tooth cutting cycle while the wheel 81 makes only one-half turn and the gear 83 one turn. During each indexing action, the drive element 79 accelerates the driven wheel 81 from a standstill to maximum velocity and then decelerates it to a standstill.

For modifying or varying the eration of the work gear, a cam drive is provided for the carrier of differential planet gear 39. The modified roll cam, designated 84, is driven from shaft 41 of the generating train through bevel gears 85, change gears 86, and worm and wheel 87. The cam reciprocates a rack 88 to thereby oscillate a meshing pinion 89. This oscillatory motion is imparted to the carrier of differential planet gear 39 through gears 90. In the event the modi fied roll action is not required for the gears to be cut, the last one of change gears 86 is replaced by a clamp which holds the shaft of worm 87 against rotation.

In cutting pinions of usual tooth number, where the work spindle is required to turn through an angle only several times that through which the cradle is turned, the drive described above is satisfactory inasmuch as there is an overall gearing-down from the main generating train drive shaft, 35, to the work spindle 15. However when cutting pinions of low tooth number, as for high reduction drives, the work spindle is required to turn through an angle many times as great as the cradle rotation angle, so that substantial gearing-up is required. In a conventional machine the fixed gearing is such that the final cradle drive ratio (of gears 34, 33) is a 30:1 reduction, the final work spindle drive (of gears 55, 56) is a 45:1 reduction, and the ratio-o-f-roll change gears 42 are seratio of [roll during gen- 3 lected by the formula NC/SO and the index gears by the formula 22.5/N, Where NC is the number of teeth in the generating gear (represented by the cutter on the cradle) and N is the number of teeth in the work gear. Thus for generating a ten-tooth pinion to mesh with a thirty-nine tooth non-generated gear, the ratio of gears 42 (of shaft 41 to shaft 43) would be 39:50 While that of index change gears 54 would be 22.5 :10, the latter being a modest gearing-up and satisfactory in view of the final reduction by gears 55, 56. However where the work pinion has only two teeth, the change gears 54 would have to provide a ratio of 22.5 to 2, a gearing-up so great as to cause roughness in the drive, with resulting poor quality of the work pinion.

In order to obviate high gearing-up, especially in the index gears 54, the index mechanism is modified to rotate gear 83 (and the carrier for differential gear 45) through three complete turns during each tooth cutting cycle, compared with only one complete turn in a conventional machine. As a result the ratio of change gears 42 is made 3NC/50 and that of index gears is reduced to 7.5/N, which means that in the most severe case (of a two-tooth pinion), the index gears have a ratio of only 7.5/2. Furthermore to prevent high gearing-up throughout the generating train an auxiliary drive for the train is provided at a point therein much closer to the work spindle than in conventional machines. This drive comprises an adjustable speed, reversible, electric motor 91, arranged to operate forwardly at low speed to eflfect the generating motion and to operate reversely at high speed to effect the return motion. The motor is connected to shaft 43 through bevel gears 92 and 93 and cylindrical gears 9'4. As this point of drive of the generating train is located between the work spindle and the reduction gears 37, 36, the drive to the work spindle involves substantially less gearing-up, and the drive to the cradle even more gearing-down, than in the conventional drive of shaft 35 by cam 57. The auxiliary motor 91 is coordinated, by means described hereinafter, with an electromagnetic clutch 95 for connecting or disconnecting shafts 62, 62.

Relative infeed and withdrawal between the cutter spindle and the work spindle, to enable the cutter to be brought into the desired cutting depth relative to a work piece, and to be clear of the work during indexing, loading and unloading of the work, is effected by the aforementioned motion 25, FIG. 1, of the sliding base 23 on frame 10. The means for producing this motion, shown in FIG. 3, include alternatively used feed paths 96 and 97 on cam 57, a cam-operated feed lever 98, and a piston-cylinder device 99 which is reciprocated in the frame by the cam and lever. The lever has follower rollers 1'01 and 102 which are so adjustable thereon that either one or both of them may be disengaged from the cam, roller 101 being engaged in track 96 when conventional gears of usual tooth number are to be generated, roller 102 being engaged in track 97 when a special pinion of the kind shown in FIG. 4 is to be produced, and neither roller being engaged when other pinions of low tooth number are being generated. The lever is pivoted to the frame 10 at 103 and has a slot 104 in which a block 105 is adjustable to various distances from the pivot. The block carries a pivot pin 106 engageable in a transverse slot 107 in cylinder member 108 of device 99. Hence by adjustment of block 105 the'magnitude of the feed motion effected by cam track 96 or 97 may be varied. The cylinder 108 itself is slidable, as a plunger, in a cylindrical chamber in the frame 10. The piston of device 99, designated 10-9, is connected to slide 23 by piston rod 110, so that motion of the piston in the cylinder is imparted to the slide, and is superimposed upon motion imparted to the slide from the cam track 96 or 97. Rod 110 also extends into an auxiliary cylinder of device 99, designated 111, which is secured to cylinder 108 and has a piston 11 2 slidable therein. A stem 113 of the piston protrudes through the head of cylinder 11 1 and has a nut 114 adjustable thereon for the purpose of adjusting the stroke of the piston.

Several switches and valves for con-trolling and coordinating the afore-described mechanisms will be referred to in the following description of typical gear cutting operations of the machine, made primarily with reference to FIGS. 2 and 3.

For generating pinions with one to four teeth, the drive of the generating train by the cam 57 is disabled by removal of one of the gears 74, and for one-tooth pinions the index also is disabled by disconnecting driver 79 and locking up the driven member 81. For pinions with two to four teeth the shifter mechanism for the index driver 79 is disabled so that the driver remains engageable with the driven member and hence turns the gear 83 three turns for each turn of cam 57. With the sliding base 23- with drawn, the cradle at the bottom of its downroll (its clockwise limit position in FIGS. 1 and 2), both follower rollers 101 and 102 disengaged from the cam 57, and lever 98 clamped to the frame (by means not shown), a work gear W is chucked on spindle 1'5 and the main motor 26 started to drive the cutter C. By means of solenoid 'operated valve 115 hydraulic pressure is applied through line 117 to the right chamber of cylinder 108 to move the piston 109 to the left through its full stroke until rod abuts piston 1 12 and the latter abuts the head of cylinder 111, to thereby advance the sliding base 23 from loading position to cutting position. Hydraulic fluid displaced from the left chamber of cylinder 108 exhausts through line 118 and valve 115. Manually operated valves 1-19 and 121 are respectively open and shut for this gear cutting operation, so that fluid may exhaust freely from cylinder 11 1 through lines 122 and 123.

Upon full advance of the sliding base 23 a limit switch 124 is actuated by a dog 125 on the sliding base to cause forward operation of auxiliary motor 91, which drives the generating train and thereby causes uproll (counterclockwise rotation) of the cradle and clockwise rotation of the work spindle, during which one tooth slot of the work 'gear is generated by the cutter C. At the conclusion of the cradle uproll, a limit switch 126 is actuated by a dog 127, which is adjustable on the cradle, to arrest the motor 91 and reverse the valve 115, the latter resulting in the piston 109 being moved to the right and the sliding base 23 withdrawn. At the conclusion of such Withdrawal a limit switch 128 is actuated by dog 125 to simultaneously energize (engage) clutch 95 and cause reverse operation of motor 91 to eifect return rotation of the generating train. The engagement of clutch 95 causes rotation of cam 57 and actuation of the index mechanism 79, 81 with the result that the work spindle is advanced to bring the next tooth space of the work pinion (if this pinion has more than one tooth) into position for cutting. With one-tooth pinions there is no indexing.

Upon completion of one turn of cam 57 'a dog 129 thereon actuates switch 131 to de-energize (disengage) clutch 95, thereby arresting the drive to the index and cam 57; and upon the completion of the return rotation of the generating train, which occurs at about the same time, the motor 91 is stopped by actuation of switch 126 by a dog 132 which is adjustable on the cradle. Such actuation of both switches 131 and 126 causes repetition of the cutting cycle, beginning with reversal of valve and thereby the advance of the sliding base 23 by piston 109, unless the last tooth (or single tooth) of the work gear has been cut, in which case an automatic stop switch, operated by a counter driven in time with cam 57, stops the machine.

The gearing shown in FIG. 4 is of the general kind disclosed and claimed in application Serial No. 854,362, filed November 20, 1959, by E. F. Elman and C. B. King, now Patent No. 2,953,031, granted September 20, 1960. It is especially adapted for automotive steering mechanisms and is characterized by providing a varying drive ratio and varying backlash. That is, the reduction ratio between pinion P and the gear or gear segment, G, which has a single circular tooth T meshing the tooth slot of the pinion, is about 16.5 :1 in the on-center position shown in FIG. 4, which is the position of FIG. 5, but decreases as indicated by ratio line 130 to about 10.5 to .1 when the gear segment has been turned about its rotation axis 133 in either direction through an angle of about fiftten degrees from the on-center posit-ion. The ratio then remains constant throughout rotation of thegear segment to its right and left limit positions, about thirty-two degrees in either direction from the on-center position. The central portion of the tooth slot of the pinion, the portion which engages the gear segment during the central fourteen degrees of the latters travel between positions 134 and 135 in FIG. 5, is slightly reduced in width, to thereby reduce backlash between the gears when at and near their oncenter position.

The varying ratio is obtained in the generation of the pinion by a corresponding varying ratio between the rotation of the work spindle 15 and the cradle 11, by means of the modified-roll cam 84 which, being driven by change gears 86 during the generating process, acts through rack and pinion 88, -89 and diiterential 35, 39, 40 to vary the rate of rotation of the cradle, assuming that the work spindle is driven at constant velocity by motor 91. The reduction in pinion slot width is obtained by withdrawal of the sliding base by cam track 97, follower roller 102 and lever 98. For this purpose cam 57 is made to turn through one complete turn between positions 136 and 137 in FIG. 5. In this view line 138 represents a plane development of the entire closed cam path 97 which is so shaped as to begin withdrawal of the sliding base in position 139, end withdrawal at 134, begin advance at 135 and end advance at 141.

In generating such a pinion P, the operating cycle of the machine is as follows, reference being primarily to FIGS. 2 and 3: With valve 119 shut and valve 121 open, the index driver 7 9 disconnected and driven member 81 locked up, and the sliding base 26 withdrawn, a pinion blank is chucked on the work spindle (in place of pinion W, FIG. 1), the main motor 26 is started and valve 115 is actuated to connect lines 116 and 117 to the hydraulic pressure source. Pressure from line 116 urges cylinder 108 to the right and thereby maintains the follower 162 against the right wall of cam track 97; and pressure from line 117 rapidly advances the sliding base 23 to cutting position. However before actual cutting starts, piston rod 110 abuts auxiliary piston 112. Further advance of the piston, to bring die work into full-cutting-depth relation to cutter C, is at a controlled slower rate desired for initial cutting without generation. This controlled rate is obtained by the discharge of the fluid from auxiliary cylinder 111 through line 122, valve 121 and valve 115 being throttled by an adjustable throttle valve 142. When the sliding base has been fully advanced, switch 124 is actuated to cause forward rotation of motor 91 and hence uproll of the cradle to generate the tooth slot. When generation has reached position 136, FIG. 5, a limit switch 14-3 is actuated by a dog 144, which is adjustably mounted on the cradle, and such actuation causes energization (engagemerit) of clutch 95 which then drives the cam 57 through one turn during which it acts through cam track 57 (138 in FIG. 5) to slightly withdraw and then advance the sliding base to narrow only the central portion of the pinion tooth slot. The change gears 59 are made of such ratio, in view of the speeds of motors 26 and 91, that the cam 57 will complete one turn by position 137, FIG. 5, at which time switch 131 is actuated to de-energize (disengage) clutch 95 and hence arrest rotation of the cam. The generating motion continues until a switch 145 is actuated by adjustable dog 146 on the cradle (the switch 126 not being effective in this cutting method) which causes arrest of generating train drive motor 91 and reversal of valve 115 to cause withdrawal of sliding base 23. Upon completion of the withdrawal switch 128 is actuated to reverse operation of the generating train by motor 91. This continues until adjustable dog 147 on the cradle reverses switch 145 to thereby stop the motor 91. The cam 57 completes a second turn whereupon the counter-operated automatic stop switch causes the main motor 26 to stop.

For generating conventional gears of usual tooth number the motor 91 is not employed, and one of gears 94 is removed. Valve 119 is open and valve 121 is shut. The index shifter mechanism is made operable, so that for each revolution of cam 57 the gear 83 is given only one turn. Clutch is mechanically locked so that cam 57 and the index drive shaft 78 are driven directly by main motor 26. The generating track 58 of cam 57 drives the generating train through the gearing previously described including gears 74 and 75. Follower roller 10 1 is engaged in track 96 of cam 57 which acts to withdraw the sliding base preceding each indexing operation, such indexing occurring during return roll of the generating train. After a blank gear W is chucked on the work spindle a manually operated reversing valve 148 is actuated to cause advance of the sliding base by piston 109. At the conclusion of such advance the main motor 26 is started and remains in operation until completion of the return roll following cutting of the last tooth, at which time it is stopped by the counter-operated automatic stop switch. Thereupon the sliding base 213 may be withdrawn by manual reversal of valve 148.

Referring now to the wiring diagram, FIG. 6, in order to condition the machine for cutting pinions of low tooth number, a selector switch 149' is opened and a selector switch 151 is closed. Opening of switch 149 de-energizes selector relay SR whose contacts SR1 and SRZ close and whose contacts SR-3 and 813-4 open. To operate the machine in this condition start switch 152 is momentarily closed, and inasmuch as manual stop switch 158 is closed, a circuit is established across alternating current leads L 1 and L-Z through controller M for the main motor 26. The controllers holding contacts M 1 and contacts M Z now close. An automatic cycle start switch 153 is momentarily closed, and since the related stop switch 161 is closed, a control relay 1R is energized, closing its holding contacts 1R1 and also contacts 1R-2. Relays 2R and SR are energized so that their contacts 2R-1 are closed, contacts ZR-Z are opened, and contact 3R-1 are closed. The sliding base in solenoid 154 for valve now is energized and the valve actuated to advance the sliding base 23. This closes switch 124, cuergizing relay 4R whose contacts 411-1 close to connect relay 5R across direct current leads L-3 and L-4. This relays contacts 5R-1 and SR-2 now closed while cont-acts 5R-3 open, energizing armature MA of motor 91, causing uproll to proceed at a rate that is adjustable by means of rheostat 157 and that is rendered low by adjustable resistance 160 in the armatures forward drive circuit. At the end of the uproll, limit switch 126 closes its contact 126-A energizing relay 6R. This closes contacts 6R- 1 and GR-S and opens contacts 6R-2, 6R-3 and 6R-4. Opening of 6R2 de-energizes relay 5R so that its contacts 5R4 and 5R2 are opened while contacts 5R-3 are closed. This places t.e armature MA in circuit with a resistor 155 and, since the field winding F of the motor is energized continuously, the motor acts to brake the generating train to a standstill. At the same time the sliding base out solenoid 156 of valve 115 is energized by the closing of contact 6R-4 and thereby withdraws the sliding base. Now sliding base out switch 128 is closed, energizing relay 7R. Contact-s 7R4. and 7R2 are closed so that relay 8R is energized. Its contacts SR-l and 8R-2 are closed, and contacts 8R-3 are opened. The motor armature MA is thus disconnected from resistance 155 and is reversely connected across leads L-3 and L4, and effects return rotation of the generating train at a fast rate.

Simultaneously, the energization of relay 7R has closed its contacts 7R-2, energizing a time relay TR of a type which when energized immediately closes its contacts TR-1 and then opens them with delay. The closing of TR1 energizes clutch 95, so that motor 26 now drives the index and the feed cam 57. As soon as the cam starts to turn, switch 131 opens, de-energizing relay 2R and closing contacts 2R-2 so that the delayed opening of contacts TR-1 is without immediate effect. However, upon completion of one revolution of the feed cam the hnnt switch 131 is again closed, energizing relay 2R and opening contacts 2R-2, and since contacts TR-1 are now open, the clutch 95 is de-energized.

At about this same time the motor 91 is stopped by the downroll switch 126 being shifted from contact 126-A to contact 126-B. This de-energizes relay 6R, opening contacts 6R-1 to de-energize relay 8R, thereby opening contacts 8R-1 and 8R2 and closing contacts SR-3 so that the motor becomes a brake. When switch 131 is closed (by completion of one revolution of cam 57) and the downroll switch 126 has shifted to contact 126B (upon completion of the downroll), the solenoid 154 is energized to advance the sliding base and repeat the cycle, unless all teeth of the pinion have been out. In this event the counter-operated automatic stop switch 159 opens to stop the machine.

It will be noted that during the above-described operation, the fact that the relay contacts SR-3 and SR4 are open renders the switches 143- and 1-45 completely ineffective.

In order to condition the machine for cutting the varying ratio steering pinion P of FIG. 4, the selector switches 151 and 149 are both closed. Relay SR is energized and its contacts SR-l and SR-2 open and contacts SR-3 and SR-4 close. This means that switches 143 and 145 are made effective while switch 126 is made ineffective. Operation of the machine is begun, as before, by momentarily closing start switches 152 and 153. When the generation reaches position 136, FIG. 5, dog 144 on the cradle moves switch 143 against its contact 143-A, energizing time relay TR and as a result, also clutch 95, causing the cam 57 to make one turn to produce narrowing of the tooth slot, as before described, and, at the end of the turn, the switch 131 is closed, to de-enengize the clutch and stop the cam rotation. The generation continues until switch 145 contacts 145-A, energizing relay 6R, so that the motor 91 is braked as before, the sliding base is withdrawn, and the motor 91 is reversed to effect return rotation of the generating train. The dog 144 on the cradle now closes the switch 143 against contact 143-B, energizing the time relay TR and the clutch 95, again starting rotation of the cam 57. At the completion of one revolution of this cam, the switch 131 is closed, and, as before, deenergizes the clutch and thereby stops cam rotation. Completion of this second rotation of the cam results, through the automatic counter, in opening of stop switch 159 to de-energize controller M and then stop main motor 26 and disable solenoid 154, and also, through opening of contacts M2, de-enengizes automatic cycle relay 1R. However the return rotation of the generating train by motor 91, if not before completed, continues until cradle carried dog 147 closes switch 145 against contact 145-13, de-energizing solenoid GR, and thereby also solenoid 8R, to disconnect the armature MA from leads L-3 and L-4 and place it in circuit with resistor 155 to brake the motor to a stop.

In order to electrically condition the machine to generate gears of usual tooth number, the switch 151 is opened. This renders the controller M for main motor 25 subject only to the control of start and stop switches 152 and 158 and automatic stop switch 159.

Having now described the improved machine and alternative methods of operating it, what is claimed as the invention is:

1. An intermittent indexing gear generator having a rotatable cradle, a cutter spindle and a Work spindle of which one is carried by the cradle, a generating lgear train connectiing the cradle and work spindle for simultaneous rotations about their respective axes at predetermined velocity ratio, an indexing drive for said work spindle connectible to said gear train through a differential gear set in said gear train, ratio-of-roll change gears in said generating train between the cradle and said ditferential gear set, a first reversible motor drive adapted to drive said train at a point therein between the cradle and said change gears, and a second reversible motor drive adapted to drive said train at a point therein between said differential gear set and said change gears.

2. A gear generator according to claim 1 in which one of said reversible motor drives comprises a motor, a cam driven unidirectionally by the motor, and a carnfollower driven alternately forward and reversely by the cam and connected to the generating train.

3. An intermittent indexing gear generator having a rotatable cradle carrying a cutter spindle, and having a work spindle connected to the cradle by a generating gear train for eifect-ing simultaneous rotations of the cradle and work spindle about their respective axes at predetermined velocity ratio, an indexing drive for said work spindle 'connectible to said gear train through a differential gear set in said gear train, ratio-of-roll change gears in said generating train between the cradle and said differential gear set, a first reversible motor drive adapted to drive said train at a point therein between the cradle and said change gears, and a second reversible motor drive adapted to drive said train at a point therein between said differential gear set and said change gears.

4. A gear generator according to claim 3 in which one of said reversible motor drives comprises a motor, a cam driven unidirectionally by the motor, and a cam follower driven alternately forwardly and reversely by the cam and connected to the generating train.

5. A gear generator according to claim 3 in which there are means to operate said second motor drive alternately forwardly and reversely, and coordinating means to cause operation of said index mechanism by said first drive during the reverse operation of said second motor drive.

6. A gear generator according to claim 5 in which the drive motor of said first drive is connected to the cutter spindle for driving the same, there is a clutch between said motor and said index mechanism, and said coordinating means is arranged to operate the index mechanism by effecting engagement of said clutch. 7. A gear generator for operation by the intermittent indexing method and having a rotatable cradle, a cutter spindle and a work spindle of which one is carried by the cradle, a generating train connecting the cradle and the work spindle for simultaneous rotations about their respective axes at predetermined velocity ratio, a reversible motor connected to said train for driving the same alternately forwardly and reversely, an index means comprising a second motor connected to said train through a differential gear set in said train, and coordinating means for causing operation of said index means to effect indexing rotation of the work spindle in predetermined phase relationship to operation of the generating train by said reversible motor.

8. A gear generator according to claim 7 in which there is a means for effecting relative withdrawal and advance between the cutter spindle and the work spindle, and said coordinating means is arranged to cause such withdrawal and advance to respectively precede and follow said operation of said index means.

9. A gear generator according to claim 8 in which said means for effecting relative withdrawal and advance comprises a hydraulic cylinder-piston device controlled by said coordinating means.

10. A gear generator according to claim 7 in which there is a means including a cam driven by said second motor for effecting relative withdrawal and advance between the cutter spindle respectively preceding and following the indexing rotation of the work spindle.

ll. A gear generator according to claim 7 in which said indexing drive further includes a first member rotated by said second motor and a second member for driving an element of said dififerential gear set, said first and second members being so arranged that during rotation of the first the second is accelerated from a standstill to a maximum velocity and then decelerated to a standstill.

12. A gear generator having a rotatable cradle, a cutter spindle and a Work spindle of which one is carried by the cradle, a generating train connecting the cradle and the work spindle for simultaneous rotations about their respective axes at predetermined velocity ratio, a reversiible motor connected to said train for driving the same alternately forward and reversely, respectively for effecting generation of a tooth slot in a workpiece on said work spindle and for return motions of the cradle and work spindle, another motor and a cam driven thereby for effecting relative withdrawal and advance between the cutter spindle and the work spindle, and coordinating means to cause such Withdrawal and advance to occur during forward rotation of the generating train respectively before and after the midpoint of such generation to thereby efiect narrowing of the central portion of the tooth slot.

{13. A gear generator according to claim 12 in which there is a second cam which is driven by said generating train, and means actuated by said second cam, including one element of a difierential gear set in said train, for increasing and decreasing the rate of rotation of the work spindle relative to the cradle respectively during the approach to and the departure from said midpoint of generation.

14. A gear generator according to claim '12 in which said means actuated by the cam includes a hydraulic cylinder-piston device to efiect advance and withdrawal between the cutter spindle and the work spindle, and said coordinating means are arranged to also control said device to effect such advance and withdrawal respectively before and after said generation.

15. A gear generator according to claim 14 in which there is a hydraulic restrictor associated with said cylinderpiston device for controlling the rate of relative advance effected thereby between the cutter spindle and the work spindle, and said coordinating means is arranged to cause forward operation of said reversible motor to occur at the conclusion of such advance.

16. A gear generator having a rotatable cradle, a cutter spindle and a work spindle of which one is carried by the cradle, a motor connected to the cutter spindle for rotating the same, a generating train connecting the cradle and the work spindle for simultaneous rotations about their respective axes at predetermined velocity ratio, a reversible motor connected to said train for driving the same alternately forwardly and reversely, an indexing drive for the work spindle including a differential gear set in said train and a clutch for connecting one element of said gear set to the first-mentioned motor for drive thereby, and coordinating means for efiecting engagement and disengagement of said clutch in predetermined phase relation to drive of the said train by said reversible motor.

17. A gear generator according to claim 16 in which said indexing drive further includes a first member rotated by said clutch and a second member for driving said element of the gear set, said first and second members being so arranged that during rotation of the first the second is accelerated from a standstill to a maximum velocity and then decelerated to a standstill.

18. A gear generator having a rotatable cradle, a cutter spindle and a work spindle of which one is carried by the cradle, a motor connected to the cutter spindle for rotating the same, a generating train connecting the cradle and the work spindle for simultaneous rotations about their respective axes at predetermined velocity ratio, a reversible motor connected to said train for driving the same alternately forwardly and reversely, a feed cam for effecting relative withdrawal and advance between the cutter spindle and the work spindle, a clutch for connecting said cam to the first-mentioned motor for drive thereby, and coordinating means for effect-ing engagement and disengagement of said clutch in predetermined relation to drive of the said train by said reversible motor.

References Cited in the file of this patent UNITED STATES PATENTS 2,034,765 Miller Mar. 24, 1936 2,725,792 Wildhaber Dec. 6, 1955 2,895,384 Baxter et al. July 21, 1959 2,953,068 Carlsen Sept. 20, 1960 FOREIGN PATENTS 497,519 Italy Sept. 15, 1954 

1. AN INTERMITTENT INDEXING GEAR GENERATOR HAVING A ROTATABLE CRADLE, A CUTTER SPINDLE AND A WORK SPINDLE OF WHICH ONE IS CARRIED BY THE CRADLE, A GENERATING GEAR TRAIN CONNECTING THE CRADLE AND WORK SPINDLE FOR SIMULTANEOUS ROTATIONS ABOUT THEIR RESPECTIVE AXES AT PREDETERMINED VELOCITY RATIO, AN INDEXING DRIVE FOR SAID WORK SPINDLE CONNECTIBLE TO SAID GEAR TRAIN THROUGH A DIFFERENTIAL GEAR SET IN SAID GEAR TRAIN, RATIO-OF-ROLL CHANGE GEARS IN SAID GENERATING TRAIN BETWEEN THE CRADLE AND SAID DIFFERENTIAL GEAR SET, A FIRST REVERSIBLE MOTOR DRIVE ADAPTED TO DRIVE SAID TRAIN AT A POINT THEREIN BETWEEN THE CRADLE AND SAID CHANGE GEARS, AND A SECOND REVERSIBLE MOTOR DRIVE ADAPTED TO DRIVE SAID TRAIN AT A POINT THEREIN BETWEEN SAID DIFFERENTIAL GEAR SET AND SAID CHANGE GEARS. 